Thermally stable light-sensitive compositions with o-quinone diazide and phenolic resin

ABSTRACT

A phenolic resin composition comprising units of formula (I): ##STR1## wherein R 1  is a halogen and R 2  is a lower alkyl group having 1 to 4 carbon atoms and said units of formula (I) are made by condensing the corresponding halogen-substituted resorcinol of formula (A): ##STR2## wherein R 1  is defined above, with the corresponding para-lower alkyl-substituted 2,6-bis(hydroxymethyl)-phenol of formula (B): ##STR3## wherein R 2  is defined above, and wherein the mole ratio of A:B is from about 0.5:1 to 1.7:1. This phenolic resin may be mixed with photoactive compounds (e.g. 1,2-naphthoquinone diazide sensitizers ) to prepare a light-sensitive composition useful as a positive-working photoresist.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to selected thermally stable phenolicresins and their use in light-sensitive compositions. In particular, thepresent invention relates to phenolic resins containing at least oneunit which is a condensation products of selected para loweralkyl-substituted 2,6-bis(hydroxymethyl)-phenols with selectedhalogen-substituted resorcinol compounds. Furthermore, the presentinvention relates to light-sensitive compositions useful aspositive-working photoresist compositions, particularly, thosecontaining these resin and o-quinonediazide photosensitizers. Stillfurther, the present invention also relates to substrates coated withthese light-sensitive compositions as well as the process of coating,imaging and developing these light-sensitive mixtures on thesesubstrates.

2. Description of Related Art

Photoresist compositions are used in microlithography processes formaking miniaturized electronic components such as in the fabrication ofintegrated circuits and printed wiring board circuitry. Generally, inthese processes, a thin coating or film of a photoresist composition isfirst applied to a substrate material, such as silicon wafers used formaking integrated circuits or aluminum or copper plates of printedwiring boards. The coated substrate is then baked to evaporate anysolvent in the photoresist composition and to fix the coating onto thesubstrate. The baked coated surface of the substrate is next subjectedto an image-wise exposure of radiatiion. This radiation exposure causesa chemical transformation in the exposed areas of the coated surface.Visible light, ultraviolet (UV) light, electron beam and X-ray radiantenergy are radiation types commonly used today in microlithographicprocesses. After this image-wise exposure, the coated substrate istreated with a developer solution to dissolve and remove either theradiation-exposed or the unexposed areas of the coated surface of thesubstrate.

There are two types of photoresist compositions--negative-working andpositive-working. When negative-working photoresist compositions areexposed image-wise to radiation, the areas of the resist compositionexposed to the radiation become less soluble to a developer solution(e.g. a cross-linking reaction occurs) while the unexposed areas of thephotoresist coating remain relatively soluble to a developing solution.Thus, treatment of an exposed negative-working resist with a developercauses removal of the non-exposed areas of the resist coating and thecreation of a negative image in the photoresist coating, and therebyuncovering a desired portion of the underlying substrate surface onwhich the photoresist composition was deposited. On the other hand, whenpositive-working photoresist compositions are exposed image-wise toradiation, those areas of the resist composition exposed to theradiation become more soluble to the developer solution (e.g. arearrangement reaction occurs) while those areas not exposed remainrelatively insoluble to the developer solution. Thus, treatment of anexposed positive-working resist with the developer causes removal of theexposed areas of the resist coating and the creation of a positive imagein the photoresist coating. Again, a desired portion of the underlyingsubstrate surface is uncovered.

After this development operation, the now partially unprotectedsubstrate may be treated with a substrate-etchant solution or plasmagases and the like. This etchant solution or plasma gases etch theportion of the substrate where the photoresist coating was removedduring development. The areas of the substrate where the photoresistcoating still remains are protected and, thus, an etched pattern iscreated in the substrate material which corresponds to the photomaskused for the image-wise exposure of the radiation. Later, the remainingareas of the photoresist coating may be removed during a strippingoperation, leaving a clean etched substrate surface. In some instances,it is desirable to heat treat the remaining resist layer after thedevelopment step and before the etching step to increase its adhesion tothe underlying substrate and its resistance to etching solutions.

Positive-working photoresist compositions are currently favored overnegative-working resists because the former generally have betterresolution capabilities and pattern transfer characteristics.

Photoresist resolution is defined as the smallest feature which theresist composition can transfer from the photomask to the substrate witha high degree of image edge acuity after exposure and development. Inmany manufacturing applications today, resist resolution on the order ofone micron or less are necessary.

In addition, it is generally desirable that the developed photoresistwall profiles be near vertical relative to the substrate. Suchdemarcations between developed and undeveloped areas of the resistcoating translate into accurate pattern transfer of the mask image ontothe substrate.

One drawback with positive-working photoresists known heretofore istheir limited resistance to thermal image deformation. This limitationis becoming an increasing problem because modern processing techniquesin semiconductor manufacture (e.g. plasma etching, ion bombardment)require photoresist images which have higher image deformationtemperatures (e.g. 150° C.-200° C.). Past efforts to increase thermalstability (e.g. increased molecular weight) generally caused significantdecrease in other desirable properties (e.g. decreased photospeed ordiminished adhesion or reduced contrast).

Accordingly, there is a need for improved positive-working photoresistformulations which produce images that are resistant to thermaldeformation at temperatures of about 150° to 200° C. while maintainingthe other desired properties (e.g. photospeed) at suitable levels. Thepresent invention is believed to be an answer to that need.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a phenolic resincomposition comprising at least one unit of formula (I): ##STR4##wherein R₁ is a halogen and R₂ is a lower alkyl group having 1 to 4carbon atoms and said unit or units of formula (I) are made bycondensing the corresponding halogen-substituted resorcinol of formula(A): ##STR5## wherein R₁ is defined above, with the correspondingpara-lower alkyl-substituted 2,6-bis(hydroxymethyl)-phenol of formula(B): ##STR6## wherein R₂ is defined above, and wherein the mole ratio ofA:B is from about 0.5:1 to 1.7:1.

Moreover, the present invention is directed to a photosensitivecomposition comprising an admixture of o-quinonediazide compound andbinder resin comprising at least one unit of the formula (I), above; theamount of said o-quinonediazide compound or compounds being about 5% toabout 30% by weight and the amount of said binder resin being about 60%to 95% by weight, based on the total solid content of saidphotosensitive composition.

Still further, the present invention also encompasses the process ofcoating substrates with these light-sensitive compositions and thenimaging and developing these coated substrates.

Also further, the present invention encompasses said coated substrates(both before and after imaging) as novel articles of manufacture.

DETAILED DESCRIPTION

The resins containing the units of formula (I) are preferably made byreacting the halogen-substituted (i.e., F, Cl, Br or I) resorcinolcompound of formula (A) with the para-lower alkyl-substituted2,6-bis(hydroxymethyl)-phenol compound of formula (B), preferably in thepresence of an acid catalyst. Suitable acid catalysts include thosecommonly employed in acid condensation-type reactants such as HCl, H₃PO₄, H₂ SO₄, oxalic acid and organic sulfonic acids. The most preferredacid catalysts are the organic sulfonic acids (e.g. p-toluene sulfonicacid). Generally, it is also preferred to carry out the condensationpolymerization in the presence of an organic solvent. Suitable solventsinclude toluene, ethanol, tetrahydrofuran, cellosolve acetate,1-methoxy-2-propanol and 2-ethoxy ethanol. Preferred solvents arewater-soluble solvents such as ethanol 1-methoxy-2-propanol and 2-ethoxyethanol.

As stated above, the mole ratio of A:B may be from about 0.5:1 to about1.7:1. The preferable mole ratio of A:B is from about 0.7:1 to about1.3:1. When A is in molar excess, resins containing the units of formula(I) will more likely be terminated with A. When B is used in molarexcess, resins containing the units of formula (I) will more likely beterminated with B.

It should be noted that this condensation polymerization reactionresults in ortho-, ortho-bonding between each phenolic structure. It isbelieved this ortho-, ortho-bonding strongly influences the high thermalstability of these resins. Furthermore, the particular positioning ofthe hydroxy groups on the resin backbone is believed to positivelyaffect the strong alkali solubility characteristics.

In making the present class of resins, the precursors (A) and (B) asdefined above are preferably placed in the reaction vessel preferablyalong with the acid catalyst and solvent. The mixture is then preferablyheated to a temperature in the range from about 60° C. to about 120° C.,more preferably from about 65° to about 95° C., for the condensationpolymerization reaction to occur. The reaction time will depend on thespecific reactants used and the reaction temperature. Times from 3 to 5hours are generally suitable.

The most preferred precursor of formula (A) is 4-chlororesorcinol andthe most preferred precursor of formula (B) is2,6-bis(hydroxymethyl)-p-cresol. When these two precursors are employed,the resultant resin will contain units of formula (IA): ##STR7##

Generally, it is preferable to make resins which contain only units offormula (I), most preferably of formula (IA); however, for someapplications it may be desirable to add another phenolic compound whichwill condense with the lower alkyl-substituted2,6-bis(hydroxymethyl)-phenol compound of formula (B). One such suitablephenolic compound is selected from meta- or para-alkoxy substitutedphenols of formula (C): ##STR8## wherein R₃ is a lower alkoxy grouphaving 1 to 4 carbon atoms. Thus, when (C) is condensed with (B), thephenolic resins described above have further units of formula (II):##STR9##

The most preferred compounds of formula (C) are para- andmeta-methoxyphenol. When these two compounds are condensated with themost preferred compound of (B), namely,2,6-bis(hydroxymethyl)-para-cresol, the resultant resins will containunits of either formula (IIA) or formula (IIB): ##STR10## With the unitsrepresented by formula (IIA), ortho-, ortho-bonding occurs because themethoxy group is in the para position. With the units represented byformula (IIB), a mixture of ortho-, ortho-bonding and ortho-,para-bonding may occur because the methoxy group is in a meta position.

Regardless of the presence or absence of the further units of formula(II), the resins of the present invention preferably have a molecularweight of from about 500 to about 10,000, more preferably from about 750to about 5,000. The preferred resins have at least about 40% by weightof the units of formula (I). When resins containing formula (II) aredesired, they preferably contain from about 40% to about 80% by weightof units of formula (I) and about 60% to about 20% by weight of units offormula (II).

The above-discussed resins of the present invention may be mixed withphotoactive compounds to make light-sensitive mixtures which are usefulas positive acting photoresists. The preferred class of photoactivecompounds (sometimes called light sensitizers) is o-quinonediazidecompounds particularly esters derived from polyhydric phenols,alkyl-polyhydroxyphenones, aryl-polyhydroxyphenones, and the like whichcan contain up to six or more sites for esterification. The mostpreferred o-quinonediazide esters are derived from2-diazo-1,2-dihydro-1-oxo-naphthlene-4-sulfonic acid and2-diazo-1,2-dihydro-1-oxo-naphthalene-5-sulfonic acid.

Specific examples include resorcinol1,2-naphthoquinonediazide-4-sulfonic acid esters; pyrogallol1,2-naphthoquinonediazide-5-sulfonic acid esters,1,2-quinonediazidesulfonic acid esters of (poly)hydroxyphenyl alkylketones or (poly)hydroxyphenyl aryl ketones such as 2,4-dihydroxyphenylpropyl ketone 1,2-benzoquinonediazide-4-sulfonic acid esters,2,4,dihydroxyphenyl hexyl ketone 1,2-naphthoquinone-diazide-4-sulfonicacid esters, 2,4-dihydroxy-benzophenone1,2-naphthoquinonediazide-5-sulfonic acid esters, 2,3,4-trihydrophenylhexyl ketone, 2-naphthoquinone-diazide-4-sulfonic acid esters,2,3,4-trihydroxy-benzophenone 1,2-naphthoquinonediazide-4-sulfonic acidesters, 2,3,4-trihydroxybenzophenone1,2-naphthoquinone-diazide-5-sulfonic acid esters,2,4,6-trihydroxy-benzophenone 1,2-naphthoquinonediazide-4-sulfonic acidesters, 2,4,6-trihydroxybenzophenone1,2-naphthoquinone-diazide-5-sulfonic acid esters,2,2',4,4'-tetrahydroxy-benzophenone 1,2-naphthoquinonediazide-5-sulfonicacid esters, 2,3,4,4'-tetrahydroxy-benzophenone1,2-naphtho-quinonediazide-5-sulfonic acid esters,2,3,4,4'-tetrahydroxybenzophenone 1,2-naphthoquinone-diazide-4-sulfonicacid esters, 2,2',3,4',6'-penta-hydroxybenzophenone1,2-naphthoquinonediazide-5-sulfonic acid esters and2,3,3',4,4',5'-hexahydroxybenzophenone1,2-naphthoquinonediazide-5-sulfonic acid esters;1,2-quinonediazidesulfonic acid esters ofbis[(poly)-hydroxyphenyl]alkanes such as bis(p-hydroxyphenyl)-methane1,2-naphthoquinonediazide-4-sulfonic acid esters,bis(2,4-dihydroxyphenyl)methane 1,2-naphthoquinone-diazide-5-sulfonicacid esters, bis(2,3,4-trihydroxy-phenyl)methane1,2-naphthoquinonediazide-5-sulfonic acid esters,2,2-bis(p-hydroxyphenyl)propane 1,2-naphthoquinone-diazide-4-sulfonicacid esters, 2,2-bis(2,4-dihydroxyphenyl)propane1,2-naphthoquinone-diazide- 5-sulfonic acid esters and2,2-bis(2,3,4-tri-hydroxyphenyl)propane1,2-naphthoquinonediazide-5-sulfonic acid esters. Besides the1,2-quinonediazide compounds exemplified above, there can also be usedthe 1,2-quinonediazide compounds described in J. Kosar, "Light-SensitiveSystems", 339-352 (1965), John Wiley & Sons (New York) or in S.DeForest, "Photoresist", 50, (1975), MacGraw-Hill, Inc. (New York). Inaddition, these materials may be used in combinations of two or more.Further, mixtures of substances formed when less than all esterificationsites present on a particular polyhydric phenol,alkyl-polyhydroxyphenone, aryl-polyhydroxyphenone and the like havecombined with o-quinonediazides may be effectively utilized in positiveacting photoresists.

Of all the 1,2-quinonediazide compounds mentioned above,1,2-naphthoquinonediazide-5-sulfonic acid di-, tri-, tetra-, penta- andhexa-esters of polyhydroxy compounds having at least 2 hydroxyl groups,i.e. about 2 to 6 hydroxyl groups, are most preferred.

Among these most preferred 1,2-naphthoquinone-5-diazide compounds are2,3,4-trihydroxybenzophenone 1,2-naphthoquinonediazide-5-sulfonic acidesters, 2,3,4,4'-tetrahydroxybenzophenone1,2-naphthoquinone-diazide-5-sulfonic acid esters, and2,2',4,4'-tetrahydroxybenzophenone 1,2-naphthoquinonediazide-5-sulfonicacid esters. These 1,2-quinonediazide compounds may be used alone or incombination of two or more.

The proportion of the light sensitizer compound in the light-sensitivemixture may preferably range from about 5 to about 30%, more preferablyfrom about 10 to about 25% by weight of the non-volatile (e.g.non-solvent) content of the light-sensitive mixture. The proportion oftotal binder resin of this present invention in the light-sensitivemixture may preferably range from about 70 to about 95%, morepreferably, from about 75 to 90% of the non-volatile (e.g. excludingsolvents) content of the light-sensitive mixture.

These light-sensitive mixtures may also contain conventional photoresistcomposition ingredients such as other resins, solvents, actinic andcontrast dyes, anti-striation agents, plasticizers, speed enhancers, andthe like. These additional ingredients may be added to the binder resinand sensitizer solution before the solution is coated onto thesubstrate.

Other binder resins may also be added. Examples includephenolic-formaldehyde resins, cresol-formaldehyde resins,phenol-cresol-formaldehyde resins and polyvinylphenol resins commonlyused in the photoresist art. If other binder resins are present, theywill replace a portion of the binder resins of the present invention.Thus, the total amount of the binder resin in the photosensitivecomposition will be from about 60% to aout 95% by weight of the totalnon-volatile solids content of the photosensitive composition.

The resins and sensitizers may be dissolved in a solvent or solvents tofacilitate their application to the substrate. Examples of suitablesolvents include ethyl cellosolve acetate, n-butyl acetate, xylene,ethyl lactate, propylene glycol alkyl ether acetates, or mixturesthereof and the like. The preferred amount of solvent may be from about50% to about 500%, or higher, by weight, more preferably, from about100% to about 400% by weight, based on combined resin and sensitizerweight.

Actinic dyes help provide increased resolution by inhibiting backscattering of light off the substrate. This back scattering causes theundesirable effect of optical notching, especially where the substrateis highly reflective or has topography. Examples of actinic dyes includethose that absorb light energy at approximately 400-460 nm [e.g. FatBrown B (C.I. No. 12010); Fat Brown RR (C.I. No. 11285);2-hydroxy-1,4-naphthoquinone (C.I. No. 75480) and Quinoline Yellow A(C.I. No. 47000)] and those that absorb light energy at approximately300-340 nm [e.g. 2,5-diphenyloxazole (PPO-Chem. Abs. Reg. No. 92-71-7)and 2-(4-biphenyl)-6-phenyl-benzoxazole (PBBO-Chem. Abs. Reg. No.17064-47-0)]. The amount of actinic dyes may be up to ten percent weightlevels, based on the combined weight of resin and sensitizer.

Contrast dyes enhance the visibility of the developed images andfacilitate pattern alignment during manufacturing. Examples of contrastdye additives that may be used together with the light-sensitivemixtures of the present invention include Solvent Red 24 (C.I. No.26105), Basic Fuchsin (C.I. 42514), Oil Blue N (C.I. No. 61555) andCalco Red A (C.I. No. 26125) up to ten percent weight levels, based onthe combined weight of resin and sensitizer.

Anti-striation agents level out the photoresist coating or film to auniform thickness. Anti-striation agents may be used up to five percentweight levels, based on the combined weight of resin and sensitizer. Onesuitable class of anti-striation agents is non-ionic silicon-modifiedpolymers. Non-ionic surfactants may also be used for this purpose,including, for example, nonylphenoxy poly(ethyleneoxy) ethanol;octylphenoxy (ethyleneoxy) ethanol; and dinonyl phenoxypoly(ethyleneoxy) ethanol.

Plasticizers improve the coating and adhesion properties of thephotoresist composition and better allow for the application of a thincoating or film of photoresist which is smooth and of uniform thicknessonto the substrate. Plasticizers which may be used include, for example,phosphoric acid tri-(β-chloroethyl)-ester; stearic acid; dicamphor;polypropylene; acetal resins; phenoxy resins; and alkyl resins up to tenpercent weight levels, based on the combined weight of resin andsensitizer.

Speed enhancers tend to increase the solubility of the photoresistcoating in both the exposed and unexposed areas, and thus, they are usedin applications where speed of development is the overridingconsideration even though some degree of contrast may be sacrificed,i.e. in positive resists while the exposed areas of the photoresistcoating will be dissolved more quickly by the developer, the speedenhancers will also cause a larger loss of photoresist coating from theunexposed areas. Speed enhancers that may be used include, for example,picric acid, nicotinic acid or nitrocinnamic acid at weight levels of upto 20 percent, based on the combined weight of resin and sensitizer.

The prepared light-sensitive resist mixture, can be applied to asubstrate by any conventional method used in the photoresist art,including dipping, spraying, whirling and spin coating. When spincoating, for example, the resist mixture can be adjusted as to thepercentage of solids content in order to provide a coating of thedesired thickness given the type of spinning equipment and spin speedutilized and the amount of time allowed for the spinning process.Suitable substrates include silicon, aluminum or polymeric resins,silicon dioxide, doped silicon dioxide, silicon resins, galliumarsenide, silicon nitride, tantalum, copper, polysilicon, ceramics andaluminum/copper mixtures.

The photoresist coatings produced by the above described procedure areparticularly suitable for application to thermally grown silicon/silicondioxide-coated wafers such as are utilized in the production ofmicroprocessors and other miniaturized integrated circuit components. Analuminum/aluminum oxide wafer can be used as well. The substrate mayalso comprise various polymeric resins especially transparent polymerssuch as polyesters and polyolefins.

After the resist solution is coated onto the substrate, the coatedsubstrate is baked at approximately 70° to 115° C. until substantiallyall the solvent has evaporated and only a uniform light-sensitivecoating remains on the substrate.

The coated substrate can then be exposed to radiation, especiallyultraviolet radiation, in any desired exposure pattern, produced by useof suitable masks, negatives, stencils, templates, and the like.Conventional imaging process or apparatus currently used in processingphotoresist-coated substrates may be employed with the presentinvention.

The exposed resist-coated substrates are next developed in an aqueousalkaline developing solution. This solution is preferably agitated, forexample, by nitrogen gas agitation. Examples of aqueous alkalinedevelopers include aqueous solutions of tetramethylammonium hydroxide,sodium hydroxide, potassium hydroxide, ethanolamine, choline, sodiumphosphates, sodium carbonate, sodium metasilicate, and the like. Thepreferred developers for this invention are aqueous solutions of alkalimetal hydroxides and silicates or ethanolamine.

Alternative development techniques such as spray development or puddledevelopment, or combinations thereof, may also be used.

The substrates are allowed to remain in the developer until all of theresist coating has dissoved from the exposed areas. Normally,development times from about 10 seconds to about 3 minutes are employed.

After selective dissolution of the coated wafers in the developingsolution, they are preferably subjected to a deionized water rinse tofully remove the developer or any remaining undesired portions of thecoating and to stop further development. This rinsing operation (whichis part of the development process) may be followed by blow drying withfiltered air to remove excess water. A post-development heat treatmentor bake may then be employed to increase the coating's adhesion andchemical resistance to etching solutions and other substances. Thepost-development heat treatment can comprise the baking of the coatingand substrate below the coating's thermal deformation temperature.

In industrial applications, particularly in the manufacture ofmicrocircuitry units on silicon/silicon dioxide-type substrates, thedeveloped substrates may then be treated with a buffered, hydrofluoricacid etching solution or plasma gas etch. The resist compositions of thepresent invention are believed to be resistant to a wide variety of acidetching solutions or plasma gases and provide effective protection forthe resist-coated areas of the substrate.

Later, the remaining areas of the photoresist coating may be removedfrom the etched substrate surface by conventional photoresist strippingoperations.

The present invention is further described in detail by means of thefollowing examples. All parts and percentages are by weight unlessexplicitly stated otherwise.

SYNTHESIS EXAMPLE 1 2,6-Bis(Hydroxymethyl)-p-Cresol/4-ChlororesorcinolNovolak (1.0:1.05 Mole Ratio)

2,6-Bis(hydroxymethyl)-p-cresol (30 g, 0.178 moles), 4-chlororesorcinol(27.07 g, 0.187 moles) and p-toluenesulfonic acid monohydrate (0.8 g,0.0042 moles) were heated at 87°-90° C. for four hours in 60 mL ofstirred 2-ethoxyethanol. The reaction mixture was diluted with 250 mL2-ethoxyethanol and added dropwise to 2.4 L of stirred H₂ O. The solidwas collected by filtration, reslurried in 400 mL H₂ O, and stirredovernight. The polymer was again collected, reslurried, and filtered.The reslurrying operation was repeated twice more. The polymer wasvacuum dried to yield 50.33 g. See Tables 1 and 2 for glass transitiontemperature and alkaline dissolution data. The ortho-, ortho-linkages ofthe alternating copolymers and the terminal groups were identified by ¹³C NMR analysis.

SYNTHESIS EXAMPLE 1A

The same novolak (24.47 g) was prepared with the relative stoichiometryof Example 1 using the procedure in Example 2. See Tables 1 and 2 forglass transition temperature and alkaline dissolution data.

SYNTHESIS EXAMPLE 2 2,6-Bis(Hydroxymethyl)-p-Cresol/4-ChlororesorcinolNovolak (1:1.02 Mole Ratio)

2,6-Bis(hydroxymethyl)-p-cresol (15 g, 0.089 moles) 4-chlororesorcinol(13.15 g, 0.091 moles) and p-toluenesulfonic acid monohydrate (0.4 g,0.0021 moles) were heated in 30 mL of mildly refluxing ethanol for 3.7hours. The reaction mixture was diluted with about 60 mL ethanol andadded dropwise to about 400 mL of rapidly stirring water. Theprecipitated polymer was collected by filtration, reslurried andrefiltered 3-4 times and vacuum dried to yield 21.53 g polymer. SeeTables 1 and 2 for glass transition and alkaline dissolution data.

SYNTHESIS EXAMPLE 3 2,6-Bis(Hydroxymethyl)-p-Cresol/4-ChlororesorcinolNovolak (1:0.85 Mole Ratio)

2,6-Bis(hydroxymethyl)-p-cresol (25 g, 0.149 moles), 4-chlororesorcinol(18.26 g, 0.126 moles) and p-toluenesulfonic acid monohydrate (0.67 g,0.0035 moles) were heated for 5.5 hours at 65°-70° C. in 37 mL2-ethoxyethanol. The reaction mixture was diluted with 125 mL2-ethoxyethanol and added dropwise to 1.5 L rapidly stirring H₂ O. Thesolid was collected by filtration, reslurried in 1 L H₂ O andrefiltered. This process was repeated twice and the solid vacuum driedto yield 38.49 g. See Tables 1 and 2 for glass transition and alkalinedissolution data. The ortho-, ortho-linkages of the alternatingcopolymers and the terminal groups were identified by ¹³ C NMR analysis.

SYNTHESIS EXAMPLE 4 2,6-Bis(Hydroxymethyl)-p-Cresol/4-ChlororesorcinolNovolak (1:0.65 Mole Ratio)

2,6-Bis(hydroxymethyl)-p-cresol (25.00 g, 0.149 moles),4-chlororesorcinol (13.96 g, 0.09 moles) and p-toluenesulfonic acidmonohydrate (0.67 g, 0.0035 moles) were reacted four hours and isolatedas described in Synthesis Example 3 to yield 35 g of novolak. See Tables1 and 2 for glass transition and alkaline dissolution data. The ortho-,ortho-linkages of the alternating copolymers and the terminal groupswere identified by ¹³ C NMR analysis.

SYNTHESIS EXAMPLE 5 2,6-Bis(Hydroxymethyl)-p-Cresol/4-Chlororesorcinol3-Methoxyphenol Novolak (1:0.85:0.20 Mole Ratio)

2,6-Bis(hydroxymethyl)-p-cresol (25.00 g, 0.149 moles),4-chlororesorcinol (18.26 g, 0.127 moles), 3-methoxyphenol (3.69 g, 0.03moles) and p-toluenesulfonic acid monohydrate (0.67 g, 0.0035 moles)were reacted four hours and isolated as described in Example 3 (exceptan additional reslurry/filtration step was added) to yield 40.4 gnovolak. See Tables 1 and 2 for glass transition and alkalinedissolution data. The ortho-, ortho-linkages of the alternatingcopolymers and the terminal groups were identified by ¹³ C NMR analysis.

SYNTHESIS EXAMPLE 6 2,6-Bis(Hydroxymethyl)-p-Cresol/4-Chlororesorcinol3-Methoxyphenol Novolak (1:0.6:0.45 Mole Ratio)

Example 5 was repeated except for changing the relative proportions of4-chlororesorcinol (12.90 g, 0.089 moles) and 3-methoxyphenol (8.3 g,0.067 moles) to yield 39.7 g of novolak. See Tables 1 and 2 for glasstransition and alkaline dissolution data. The ortho-, ortho-linkages ofthe alternating copolymers and the terminal groups were identified by ¹³C NMR analysis.

SYNTHESIS EXAMPLE 7 2,6-Bis(Hydroxymethyl)-p-Cresol/4-Chlororesorcinol4-Methoxyphenol Novolak (1:0.85:0.20 Mole Ratio)

Example 5 was repeated except 3-methoxyphenol was replaced by4-methoxyphenol. The yield was 40.8 g. See Tables 1 and 2 for glasstransition and alkaline dissolution data. The ortho-, ortho-linkages ofthe alternating copolymers and the terminal groups were identified by ¹³C NMR analysis.

SYNTHESIS EXAMPLE 8 2,6-Bis(Hydroxymethyl)-p-Cresol/4-Chlororesorcinol4-Methoxyphenol Novolak (1:0.6:0.45 Mole Ratio)

Example 6 was repeated except 3-methoxyphenol was replaced by4-methoxyphenol. The yield was 39.7 g. See Tables 1 and 2 for glasstransition and alkaline dissolution data. The ortho-, ortho-linkages ofthe alternating copolymers and the terminal groups were identified by ¹³C NMR analysis.

SYNTHESIS EXAMPLES 9-132,6-Bis(Hydroxymethyl)-p-Cresol/4-Chlororesorcinol 4-MethoxyphenolNovolaks

2,6-Bis(hydroxymethyl)-p-cresol (30 g, 0.178 moles) (BHMPC),4-chlororesorcinol (see Table 3), 4-methoxyphenol (see Table 3), andp-toluenesulfonic acid monohydrate (0.8 g, 0.0042 moles) were reacted in60 ml 2-ethoxyethanol at 90°-95° C. for approximately 4 hours. Thesolutions were diluted with 250 mL of 2-ethoxyethanol and added dropwiseto 2.4 L rapidly stirring H₂ O. The polymer was collected by filtration,washed 3-4 times with H₂ O and vacuum dried. See Table 3 for yields. SeeTables 1 and 2 for glass transition and alkaline dissolution data.

SYNTHESIS COMPARISON 1 Meta-, Para-Cresol Novolak

A reference meta-, para-cresol novolak was prepared using the basicprocedure outline in Example 1 in U.S. Pat. No. 4,371,631 using afeedstock of approximately 45% m-cresol and 55% p-cresol. This was arandom copolymer and was not an alternating copolymer like thosenovolaks of Examples 1-13. The m-cresol units may link with each otherand p-cresol groups may link with each other by methylene linkages.Thus, adjacent groups in the polymer chain may be the same groups.

                  TABLE 1                                                         ______________________________________                                        Synthesis Example     Tg (°C.)                                         ______________________________________                                        1                     Note.sup. ○1                                     1A                    176                                                     2                     186                                                     3                     Note.sup. ○1                                     4                     Note.sup. ○1                                     5                     Note.sup. ○1                                     6                     Note.sup. ○1                                     7                     Note.sup. ○1                                     8                     Note.sup. ○1                                     9                     173                                                     10                    132                                                     11                    142                                                     12                    151                                                     13                    120                                                     Comparison 1          107                                                     ______________________________________                                         Note.sup. ○1 :                                                         Glass transition temperature measured up to 200° C. These novolaks     did not have an observed glass transition temperature over the measured       range and are assumed to have higher glass transition temperatures than       200° C.                                                           

                  TABLE 2                                                         ______________________________________                                        Synthesis                                                                              Dissolution Dissolution Dissolution                                  Example  Time (sec).sup. ○1  ○2                                                      Time (sec).sup. ○1  ○3                                                      Time (sec).sup. ○1  ○4         ______________________________________                                                                         9                                            1        --          13           6                                           1A       6           --          --                                           2        8           --          --                                           3        --          37          6                                            4        --          200         17                                           5        --          22          8                                            6        --          49          DND.sup. ○5                           7        --          17          7                                            8        --          52          39                                           10       --          --          7.sup. ○6a                            11       --          --          18.sup. ○6b                           12       --          --          74.sup. ○6c                           13       --          --          8                                            Comparison 1                                                                           60          63          50                                           ______________________________________                                         .sup. ○1 approximately 1 μm thick film                              .sup. ○2 LSI developer, a Sodium Silicate/Na.sub.3 PO.sub.4            developer, available from Olin Hunt Specialty Products, Inc. of East          Providence, Rhode Island (diluted 1:1 by volume with water).                  .sup. ○3 0.123 N NaOH                                                   .sup. ○4 0.3 N tetramethylammonium hydroxide                          .sup. ○5 Did not dissolve completely                                   .sup. ○6 Dissolution times were normalized to that expected for 1      μm thickness from thicker films of (a) 2.1 microns, (b) 2.45 microns,      (c) 1.2 microns                                                          

                                      TABLE 3                                     __________________________________________________________________________    4-chlororesorcinol                                                                          4-methoxyphenol                                                 (4-CR)        (4-MP)   yield                                                                            Weight Ratio                                                                              Mole Ratio                              Example                                                                            g    mole                                                                              g    mole                                                                              g  BHMPC:4-CR + 4-MP                                                                         BHMPC:4-CR:4-MP                         __________________________________________________________________________     9   20.63                                                                              0.143                                                                              8.86                                                                              0.071                                                                             53 1:0.98      1:0.80:0.40                             10   15.47                                                                              0.107                                                                             18.82                                                                              0.152                                                                             52.8                                                                             1:1.14      1:0.6:0.85                              11   15.47                                                                              0.107                                                                             14.39                                                                              0.116                                                                             50.4                                                                             1:1.1       1:0.6:0.65                              12   14.18                                                                              0.098                                                                             14.39                                                                              0.116                                                                             50.3                                                                             1:0.95      1:0.55:0.65                             13   14.18                                                                              0.098                                                                             18.82                                                                              0.152                                                                             52.2                                                                             1:1.1       1:0.55:0.85                             __________________________________________________________________________

TABLE 1

The data in Table 1 shows that novolaks prepared by this inventionexhibit high glass transition temperatures relative to conventionalnovolaks used in photoresist. (Comparison 1 vs. Examples 1-13). Also,Examples 9-12 show that as the molar ratio of 4-chlororesorcinol tomethoxyphenol in the feed decreases, the glass transition temperature ofthe resulting novolak decreases. However, the T_(g) 's remain highrelative to Comparison 1. The advantage of these high glass transitiontemperatures is that they will result in improved photoresists withhigher resistance of thermal flow.

TABLE 2

The data in Table 2 shows that novolak resins of the present inventionas prepared by Examples 1-8 and 10-13 exhibit relatively high alkalinesolubility in common photoresist developers. In most cases shown, thetime for dissolving these resins (1 μm thickness) was faster than assimilar to that of a resin coating of known cresol/formaldehyde novolak.Looking at the first Dissolution Time column, the resins produced byExamples 1A and 2 were much more soluble in a sodium silicate/Na₃ PO₄developer than the known novolak. In the second column, resins ofExamples 1, 3 and 5-8 were faster than the known novolak. Example 4 wasslower. It is believed that this slow rate was due to an undesirable(but not fully understood) cation effect between the resin and thedeveloper. In the third Dissolution Time column, the resins of Examples1, 3-5, 7, 8, 10, 11 and 13 were faster than the control. The reason whythe resin of Example 6 did not fully dissolve in the tetramethylammoniumhydroxide is not fully known, but is believed to be caused by anunwanted cation effect. Example 12 in this column has a slightly slowerdissolution time than the control. It is believed this was caused by theparticular mole ratio of reactants employed.

TABLE 3

Table 3 shows the weight and molar quantities and ratios of4-chlororesorcinol and 4-methoxyphenol used to prepare novolaks inExamples 9-13. Also shown is the weight yield of each novolak.

APPLICATION EXAMPLE 1

The novolak resin in Synthesis Example 1 (3 parts) and the condensationproduct of 1.4 equivalents of 1,2 naphthoquinone-2-diazide-5-sulfonylchloride with 1 equivalent 2,3,4-trihydroxybenzophenone (1 part) weredissolved in propylene glycol methyl ether acetate and microfiltered.The resist was spun cast upon silicon or silicon dioxide wafers andbaked at 100° for thirty minutes in a convection oven.

The solids content was adjusted to yield about one micron thick films.The resist was exposed on a Canon PLA 501F Aligner through a variabledensity mask (Optoline Type 2) and immersion developed for 60 seconds.For data see Tables 4 and 5.

APPLICATION EXAMPLES 2-7

The novolaks in Synthesis Examples 3-8 were formulated and tested as inExample 1. For data see Tables 4 and 5.

APPLICATION COMPARISON 1

The novolak in Synthesis Comparison 1 was formulated and tested as inApplication Example 1 except the solvent was 85% by weight ethylcellulose acetate, 6.5% by weight n-butyl acetate and 8.5% by weightxylene. For data see Tables 4 and 5.

                  TABLE 4                                                         ______________________________________                                        (Tetramethylammonium Hydroxide Developer)                                                                Unexposed                                                                             Sensi-                                     Application                                                                           Synthesis                                                                              Developer Film Loss                                                                             tivity.sup.( ○2 , ○3 )       Example Example  Normality (Å) (mJ/cm.sup.2)                              ______________________________________                                        1       1        0.084     250     75                                         2       3        0.084     275     75                                         3       4        0.210     475     70                                         4       5        0.108     400     75                                         5       6        0.600     .sup. ○1                                                                       --                                         6       7        0.108     325     63                                         7       8        0.600      0      100                                        Com-    Com-     0.284     300     43                                         parison 1                                                                             parison 1                                                             ______________________________________                                         .sup. ○1 A thin film of resist remained undissolved independent of     exposure.                                                                     .sup. ○2 Clean, well formed images were obtained only from Example     2 and Comparison 1                                                            .sup. ○3 Exposure dose was measured at 436,400 and 365 nm and then     summed.                                                                  

                  TABLE 5                                                         ______________________________________                                        (Sodium Hydroxide Developer.sup. ○1 )                                                             Unexposed                                          Application                                                                           Synthesis                                                                              Developer Film Loss                                                                              Sensitivity.sup. ○2                Example Example  Normality (Å)  (mJ/cm.sup.2)                             ______________________________________                                        1       1        0.031     350      125                                       2       3        0.050     375      125                                       3       4        0.135     100       75                                       4       5        0.036     300      125                                       5       6        0.063     100       94                                       6       7        0.036     125      113                                       7       8        0.075     250       75                                       Com-    Com-     0.093      40       55                                       parison 1                                                                             parison 1                                                             ______________________________________                                         .sup. ○1 All images were clean and well formed.                        .sup. ○2 Exposure dose was measured at 436,400 and 365 nm and then     summed.                                                                  

TABLE 4

Table 4 shows the unexposed film loss and sensitivity of photoresistfilms, formulated from novolaks described in Examples 1 and 3-8, afterexposure to UV radiation and subsequent latent image development withtetramethylammonium hydroxide developer. All the Examples except Example5 showed relatively desirable results in that the sensitivites of eachExample were reasonable (i.e. less than about 125 mJ/cm²) while theunexposed film loss was held under 5% of the original 1 micron filmthickness. It is not fully known why the film in Application Example 5did not completely develop, but it is believed this was caused by acation effect between the resin and the developer (See Table 2, column3, Example 6).

TABLE 5

Table 5 shows the unexposed film loss and sensitivity of photoresistfilms, formulated from novolaks described in Examples 1 and 3-8, afterexposure to UV radiation and subsequent latent image development withsodium hydroxide developer. All the examples showed relatively desirableresults in that the sensitivities of each Example were reasonable (i.e.less than about 125 mJ/cm²) while the unexposed film loss was held under5% of the original 1 micron film thickness.

Application Examples 8, 10 and 11 illustrate that different developerscan be used with this invention. Application Example 9 illustrates theexcellent stability to thermal deformation of this invention. Example 11also shows that different photoactive compounds may be used informulations of photosensitive compositions of this invention.

APPLICATION EXAMPLE 8 (Different Novolak to O-Naphthoquinone DiazideRatio and Different Developer)

Resists using novolaks prepared in Synthesis Examples 1A and 2 wereformulated as in Application Example 1 except in a 4:1 novolak too-naphthoquinone diazide ratio. The resists were then mixed in a 32%:68%ratio respectively. The resist was processed as described in ApplicationExample 1 using a 90 second immersion development in 80% HPRD-411, anethanolamine-based developer made by Olin Hunt Specialty Products, Inc.of East Providence, RI. Resist films were exposed on a MICRALIGN 111from Perkin-Elmer using a variable density mask. Unexposed film loss was550 Å with a sensitivity of 77 mJ/cm². The images were generally clean.

APPLICATION EXAMPLE 9 (Different Imaging Apparatus than ApplicationExample 8--Thermal Properties Measured)

An Ultratech Stepper 1000 was used to expose the resist in ApplicationExample 8. The resist was developed as described in Application Example8. Unexposed film loss was 200 Å. Images approximately 1.25 micronsgenerated in this manner were subjected to a convection oven bake of198°, 228° or 252° for thirty minutes. Images under all three heatingconditions showed no visible signs of deformation by scanning electronmicrograph. Exposure was 196 mJ/cm². Typical positive-working resistsbased on novolaks and o-naphthoquinone diazide ester sensitizers showimage deformation at about 130° C. or below.

APPLICATION EXAMPLE 10 (Raised Developer Strength and Lowered DevelopingTimes with Different Novolak)

The novolak from Synthesis Example 10 was formulated and tested as inApplication Example 1. When the resist was developed for 60 seconds in0.3N tetramethylammonium hydroxide, unexposed film loss was about 300 Åand photosensitivity was about 125 mJ/cm². Images were of poor quality.Cleaner, improved quality images were obtained using a 0.36Ntetramethylammonium hydroxide developer in a twenty second immersionprocess. Photosensitivity remained at about 125 mJ/cm² with no unexposedfilm loss. Excellent images were obtained with LSI developer diluted 1:3by volume with water (a solution silicate/sodium phosphate developerfrom Olin Hunt Specialty Products). Photosensitivity was 100 mJ/cm² withan unexposed film loss of about 150 Å.

APPLICATION EXAMPLE 11 (Different Sensitizer)

The novolak from Synthesis Example 11 was formulated and tested as inApplication Example 1. The photoactive component of the resist consistedof a 50:50 (W:W) mixture of the condensation products of2,3,4-trihydroxybenzophenone and 2,3,4-trihydroxyacetophenone withapproximately three equivalents each of1,2-naphthoquinone-2-diazide-5-sulfonyl chloride. Clean images wereobtained using 0.36N tetramethylammonium hydroxide developer for thirtyseconds at an exposure of 138 mJ/cm². No film loss was observed.

What is claimed is:
 1. A light-sensitive composition comprising anadmixture of at least one photosensitive o-quinonediazide compound and abinder resin comprising at least about 40% by weight of units of theformula (I): ##STR11## wherein R₁ is a halogen atom and R₂ is a loweralkyl group having 1 to 4 carbon atoms, the amount of saido-quinonediazide compound or compounds being about 5% to about 30% byweight and the amount of said binder resin being about 60% to 95% byweight, based on the total solid content of said photosensitivecomposition.
 2. The light-sensitive composition of claim 1 wherein saido-quinonediazide compound or compounds are present in the amount ofabout 10% to about 25% by weight, based on the total solid content ofsaid photosensitive composition and said binder resin is present in theamount of about 70% to about 95% by weight, based on the total solidcontent of said photosensitive composition.
 3. The light-sensitivecomposition of claim 1 wherein said o-quinonediazide compound orcompounds are selected from theo-naphthoquinone-(1,2)-diazide-4-sulfonic acid esters ando-naphthoquinone-(1,2)-diazide-5-sulfonic acid esters.
 4. Thelight-sensitive compositions of claim 3 wherein said esters are derivedfrom polyhydric phenols, alkyl-polyhydroxyphenones andaryl-polyhydroxy-phenones.
 5. The light-sensitive composition of claim 4wherein said esters are selected from the group consisting ofpolyhydroxybenzophenones and polyhydroxy-acetophenones and mixturesthereof.
 6. The light-sensitive composition of claim 1 wherein saidbinder resin has a molecular weight of about 500 to about 10,000.
 7. Thelight-sensitive composition of claim 1 wherein said units of formula (I)represent about 40% to about 80% by weight of the total binder resin. 8.The light-sensitive composition of claim 1 wherein said units of saidbinder resin is of the formula (IA): ##STR12##
 9. The light-sensitivecomposition of claim 1 wherein said binder resin has further units ofthe formula (II): ##STR13## wherein R₃ is a lower alkoxy group having 1to 4 carbon atoms and R₂ is a lower alkyl group having 1 to 4 carbonatoms.
 10. The light-sensitive composition of claim 10 wherein saidunits of formula (II) represent from 0% to about 60% by weight of thetotal binder resin in said photosensitive composition.
 11. Thelight-sensitive composition of claim 10 wherein said units of formula(II) represent from about 20% to about 60% by weight of the total binderresin in said photosensitive composition.
 12. The light-sensitivecomposition of claim 9 wherein said further units of said binder resinare of formula (IIA): ##STR14##
 13. The light-sensitive composition ofclaim 9 wherein said further units of said binder resin are of formula(IIB): ##STR15##
 14. The light-sensitive composition of claim 1 furthercomprising the presence of at least one other aqueous alkali-solublebinder resin.
 15. The light-sensitive composition of claim 14 whereinsaid other aqueous alkali-soluble binder resin is selected from aphenolic-formaldehyde resin, a cresol-formaldehyde resin and aphenol-cresol-formaldehyde resin and a polyvinyl phenol resin.
 16. Thelight-sensitive composition of claim 1 further comprising at least onesubstance selected from solvents, actinic and visual contrast dyes,plasticizers, anti-striation agents and speed enhancers.
 17. Alight-sensitive composition comprising an admixture of at least onephotosensitive o-quinonediazide compound and a binder resin comprisingunits chosen from the formulae (IA), (IIA), and (IIB): ##STR16## theamount of said o-quinonediazide compound being from about 10% to about25% by weight and the amount of said binder resin being from 70% to 90%by weight, based on the total solids contents of the light-sensitivecomposition, and wherein the units of formula (IA) comprise from about40% to 100% by weight of said binder resin and the units of formula(IIA) and (IIB) comprise from 0% to about 60% by weight of said binderresin.
 18. A coated substrate comprising a substrate coated with a filmof a light-sensitive composition comprising an admixture of at least onephotosensitive o-quinonediazide compound and a binder resin comprisingat least about 40% by weight of units of the formula (I): ##STR17##wherein R₁ is a halogen atom and R₂ is a lower alkyl group having 1 to 4carbon atoms, the amount of said o-quinonediazide compound being about5% to about 30% by weight and the amount of said binder resin beingabout 60% to 95% by weight, based on the total solid content of saidphotosensitive composition.
 19. The coated substrate of claim 18 whereinsaid substrate comprises one or more compounds selected from the groupconsisting of polyester, polyolefin, silicon, gallium arsenide,silicon/silicon dioxide, doped silicon dioxide, silicon nitride,aluminum/copper mixtures, tantalum, copper and polysilicon.
 20. Thecoated substrate of claim 18 wherein said substrate is a silicon wafercoated with silicon dioxide.